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var startTime = new GlideDateTime("2022-08-28 09:00:00");
  var endTime = new GlideDateTime("2022-08-31 02:10:00");
   // Duration in hours
  var dur_seconds = gs.dateDiff(start, end, true); // returns the number of seconds as String
  var dur_hours = Math.round(dur_seconds / 3600); // Math.round() is optional and will round the number to the nearest integer
  gs.print(dur_hours);

Output:

How to calculate difference between two dates in hours ServiceNow ?
Working Code Asked question August 22, 2023